Organic electroluminescent elements (hereinafter, also referred to as “organic EL elements”) utilizing electroluminescence of organic materials have drawn attention as display elements used for thin display devices. Organic EL elements emit light by recombining holes injected from the anode and electrons injected from the cathode within a light-emitting layer disposed between these electrodes. Such self-luminous organic EL elements have advantages such as high-luminance light emission, a high response speed, a wide viewing angle, a thin profile, and a light weight, and are therefore expected to be applied to various fields such as display panels and illumination lamps.
A light-emitting layer for organic EL elements provided to organic EL display panels is usually a mixed layer, obtained by co-deposition, of a luminescent dopant material mainly providing luminescence and a luminescent host material mainly transporting holes and electrons. Studies have been made to enhance the functionality of such organic EL elements by changing the material composition of the light-emitting layer. For example, the following organic EL elements are known.
Patent Literature 1, for example, discloses an organic EL element including a light-emitting layer which includes light-emitting portions each made of a material obtained by doping, with a luminescent dopant material, a luminescent host material which is a mixture of materials such as a material constituting a hole transport layer and a material constituting an electron-transport layer.